American Water Heater American Water Heaters Residential Gas Water Heater Danger, Mixing Valves

TYPICAL INSTALLATION

MIXING VALVE / THERMAL EXPANSION TANK USAGE AND SPACE HEATING

FIGURE 2.

Mixing Valves

heater (see Figure 3) or at hot water taps to further reduce system

water temperature.

DANGER

Water temperature over 125°F (52°C) can cause severe burns instantly resulting in severe injury or death.

Children, the elderly and the physically or mentally disabled are at highest risk for scald injury.

Feel water before bathing or showering.

Temperature limiting devices such as mixing valves must be installed when required by codes and to ensure safe temperatures at fixtures.

Mixing valves are available at plumbing supply stores. Consult a Qualified Installer or ServiceAgency. Follow mixing valve manufacturer’s instructions for installation of the valves.

TABLE 1.

Water Temperature °F	Time for 1st Degree Burns	Time for Permanent Burns
	(Less Severe Burns)	2nd & 3rd Degree
		(Most Severe Burns)
110	(normal shower temp.)
116	(pain threshold)
116	35 minutes	45 minutes
122	1 minute	5 minutes
131	5 seconds	25 seconds
140	2 seconds	5 seconds
149	1 second	2 seconds
154	instantaneous	1 seconds

Water heated to a temperature which will satisfy clothes washing, dish washing, and other sanitizing needs can scald and cause permanent injury upon contact. Short repeated heating cycles caused by small hot water uses can cause temperatures at the point of use to exceed the water heater’s temperature setting by up to 20°F (11°C).

Some people are more likely to be permanently injured by hot water than others. These include the elderly, children, the infirm and the physically/mentally disabled. Table 1 shows the approximate time- to-burn relationship for normal adult skin. If anyone using hot water provided by the water heater being installed fits into one of these groups or if there is a local code or state law requiring a certain water temperature at the point of use, then special precautions must be taken.

In addition to using lowest possible temperature setting that satisfies demand of application a Mixing Valve should be installed at water

(U.S. Government Memorandum, C.P.S.C., Peter L. Armstrong, Sept. 15, 1978)

		HOT WATER
		OUTLET
			12” TO 15”
TEMPERED WATER			(30-38 cm)
	OUTLET
COLD			CHECK
WATER			VALVE
INLET			MIXING
		CHECK
			VALVE
		VALVE

TO TANK

INLET

FIGURE 3.

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